Abstract: Magnesium phosphate cement(MPC) is used to stabilize/solidify lead-contaminated soils. Unconfined compressive strength test and permeability test are conducted to investigate the variation of mechanical properties of MPC treated lead-contaminated soils along with MPC dosage and water content. Results show that the unconfined compressive strength increased significantly with MPC dosage, while the hydraulic conductivity changed oppositely. There is a threshold value for water content of 0.45 of its influence on unconfined compressive strength and hydraulic conductivity. The unconfined compressive strength increased with the water content before the threshold value, while the hydraulic conductivity changed oppositely. “MTP” test results show that the total void volume reduce as the MPC dosage, the total void volume of soil reduce as the water content before the threshold value. SEM test results show that a larger aggregation formation, with a smaller void space in soils as the MPC dosage increase, more obvious aggregation and cementation occur in soils space as the water content less than the threshold value. These results can be attributed to the decreases of the pore volume of soil pores, which the diameter larger than 1 ?m.

Key words: solidification/stabilization(S/S), magnesium phosphate cement(MPC), lead contaminated soil, unconfined compressive strength, hydraulic conductivity, microstructure